Olefin metathesis and catalyst

ABSTRACT

Olefins are converted into other olefins having different numbers of carbon atoms by contact with a catalyst comprising an inorganic refractory oxide support containing at least one of tungsten oxide and molybdenum oxide and a promoting amount of at least one methylating agent under conditions suitable for the methylating agent compounds to promote the activity of tungsten and molybdenum oxides for the disproportionation reaction.

BACKGROUND OF INVENTION

This invention relates to the disproportionation (metathesis) ofolefins. In accordance with one aspect, this invention relates to acatalyst suitable for use in the disproportionation of olefinichydrocarbons. In accordance with another aspect, this invention relatesto a process for the disproportionation of olefinic hydrocarbons. Inaccordance with a further aspect, this invention relates to a catalystsuitable for use in the disproportionation of olefins comprising atleast one of molybdenum oxide and tungsten oxide, an inorganicrefractory oxide support, and at least one methylating agent. Inaccordance with a further aspect, this invention relates to a catalystsuitable for use in the disproportionation of olefins comprising asupport and at least one of molybdenum oxide and tungsten oxide promotedwith at least one methylating agent. In accordance with another aspect,this invention relates to a process for the disproportionation ofolefinic hydrocarbons with a disproportionation catalyst as hereinbeforedescribed under conditions of temperature and pressure which effectdisproportionation of the feed.

The disproportionation, or metathesis, of olefins is a reaction in whichone or more olefinic compounds are transformed into other olefins ofdifferent molecular weights. The disproportionation of an olefin withitself to produce an olefin of a higher molecular weight and an olefinof a lower molecular weight can also be referred to as aself-disproportionation. For example, propylene can be disproportionatedto ethylene and cis-, and trans-2-butene. Another type ofdisproportionation involves the cross-disproportionation of twodifferent olefins to form still other olefins. An example would be thereaction of one molecule of 2-butene with one molecule of 3-hexene toproduce two molecules of 2-pentene.

By the term "disproportionation" or "metathesis" throughout thisspecification is meant the conversion of the feed olefinic (orunsaturated) hydrocarbon to a mixture of olefinic (or unsaturated)hydrocarbons having different numbers of carbon atoms than the feedhydrocarbons.

Among the catalysts that have been developed for disproportionation arethose comprising inorganic refractory oxides containing a catalyticamount of at least one of molybdenum oxide and tungsten oxide. Thepresent invention is based upon the discovery of a way to improve theactivity of such a catalyst.

Accordingly, an object of this invention is to provide a method for theconversion of olefins.

Another object of this invention is to provide a catalyst for theconversion of olefins.

Still another object of this invention is to provide a method forconverting olefins to olefins having different numbers of carbon atomsthan the feed hydrocarbons.

Still another object is to provide a method for improving the activityof a disproportionation catalyst for the conversion of olefins intoolefins having different numbers of carbon atoms than the feedhydrocarbons.

Other aspects, objects and the several advantages of the invention willbe apparent to one skilled in the art upon reading the disclosureincluding a detailed description of the invention and the appendedclaims.

SUMMARY OF INVENTION

In accordance with the present invention, a disproportionation(metathesis) catalyst comprising an inorganic refractory oxidecontaining a catalytically effective amount of at least one ofmolybdenum oxide and tungsten oxide is improved by contacting thecatalyst with a promoting amount of at least one methylating agent underconditions suitable for the methylating agent to promote the activity ofmolybdenum and tungsten oxides.

Further, in accordance with a specific embodiment of the presentinvention, a disproportionation (metathesis) catalyst comprising aninorganic refractory oxide, such as silica, containing a catalyticallyeffective amount of tungsten oxide is improved by contacting thetungsten oxide catalyst with a promoting and activating amount of atleast one methylating agent, such as dimethyl sulfate, under conditionssuitable for the methylating agent to promote the activity of tungstenoxide.

Also according to the invention, a process is provided for thedisproportionation of an olefinic hydrocarbon by contacting the samewith a disproportionation catalyst as hereinbefore described underconditions of temperature and pressure which effect disproportionationof the feed.

The inorganic refractory oxide comprises solid inorganic oxide supportusually containing a major proportion of alumina or silica. Suchmaterials are commonly known as refractory oxides and include, forexample, silica, alumina, magnesia-alumina, silica-alumina,titania-alumina, zirconia-alumina, alumina-titania-zirconia, thoria,aluminum phosphate, zirconium phosphate, calcium phosphate, magnesiumphosphate, thorium phosphate, and titanium phosphate. Preferredrefractory metal oxides are silica refractory oxides, i.e., refractoryoxides containing a substantial proportion of silica, e.g., at least 90percent by weight of silica, preferably at least 99 percent of silicaalthough still larger proportions of silica can be used. Generally, therefractory oxide has a surface area of at least 10 m² /g and preferablythe surface area is from about 25 m² /g to 800 m² /g.

Molybdenum oxide and tungsten oxide can be combined with the refractoryoxide support in any conventional manner such as dry mixing,impregnation from a diluent, ion-exchange or the like. The oxides can beadded directly or in the form of molybdenum or tungsten compounds thatcan be converted to oxides by calcination.

Preferred combinations of the above support materials with the oxides ofmolybdenum and tungsten promoter materials include (1) silica or thoriapromoted by the oxide, or a compound convertible to an oxide bycalcination, of tungsten or molybdenum; (2) alumina promoted by anoxide, or compound convertible to an oxide by calcination, of molybdenumor tungsten; and (3) one or more of the group aluminum phosphate,zirconium phosphate, calcium phosphate, magnesium phosphate, thoriumphosphate or titanium phosphate promoted by one or more of an oxide ofmolybdenum or tungsten, or by a compound of molybdenum or tungstenconvertible to an oxide by calcination.

The solid component of the catalysts can be in any conventionalcatalytic shape or size, depending upon the type of conversion in whichit is to be utilized. For example, in fixed bed catalyst systems, thesolid composite can be in the form of spheres, pellets, extrudates,agglomerates, and the like. In slurry catalyst systems, the solid can bein the form of relatively small particles or in the form of a powder.

To be effective in the present catalyst system, the above-describedcomponent of the catalysts is activated at elevated temperatures,generally in flowing air. The activation of the catalysts isaccomplished at a temperature of from about 300° to about 800° C. for aperiod of several minutes to several hours or longer. When the solidcomponent of the catalyst system is tungsten oxide on silica, aconvenient and economical treatment is in the temperature range of400°-700° C. for 0.5 to 20 hours or longer. In some cases the activationusing an oxygen-containing gas can be followed by treatment, also atelevated temperatures, with other treating gases such as carbonmonoxide, hydrogen, and the like.

The oxide of molybdenum or tungsten is preferably combined with theinorganic oxide solid support in a high positive oxidation state, e.g.,hexavalent molybdenum or hexavalent tungsten. The proportion of themolybdenum or tungsten oxide combined with the inorganic oxide supportcan be varied, but generally the inorganic oxide solid contains at least0.1 percent by weight of the oxide of molybdenum or tungsten withamounts from about 0.2 percent to about 30 percent by weight beingpreferred, although still larger (major) proportions of molybdenum ortungsten oxide can be used. The weight percent referred to is based onthe combined weights of the support and the metal.

The methylating agent can be combined with the thus prepared catalyst inany suitable manner. For example, the catalyst is impregnated with aliquid diluent containing the methylating agent. After impregnation thecatalyst is then heated in an inert atmosphere, such as nitrogen orargon, to remove the liquid diluent. The temperature employed inremoving the diluent and activating can vary widely; however,temperatures in the range of about 400° C. to about 800° C. arecurrently preferred. If desired, the methylating agent can be applied tothe catalyst in a reaction zone by spraying or otherwise contacting thecatalyst. It is also contemplated that the methylating agent can beintroduced along with olefin feed for contacting with the catalyst.

The benefits provided by the methylating agent treatment are adverselyaffected if the catalyst is later exposed to an oxidative atmosphere,especially at elevated temperatures. Accordingly, preferably thecatalyst is maintained under a substantially inert atmosphere after themethylating treatment.

Examples of methylating agents that can be used according to theinvention include dimethyl sulfate, dimethylsulfoxide, trimethyloxoniumtetrafluoroborate, methyl iodide, and methyl bromide, and the like, andmixtures thereof.

The optimum amounts of methylating agent employed can readily bedetermined by routine experimentation. Generally, the methylating agentshould be used in an amount in the range of about 0.1 to about 20 weightpercent, preferably about 5 to about 15 weight percent, based on thetotal weight of the metal oxide and support prior to the addition of themethylating agent.

The promoted catalyst can be used in disproportionation reactions in aconventional manner. The reaction temperature can vary depending uponthe catalyst and feed(s) employed, but will be sufficient to effectdisproportionation. Typically, the disproportionation is carried out ata temperature in the range of about 20° to about 600° C.

The disproportionation reaction can be carried out by contacting theolefins to be disproportionated with the catalyst in the liquid phase orthe gas phase, depending on structure and molecular weight of theolefins, temperature and pressure.

Olefins applicable for use in the process of the invention arenontertiary, nonconjugated acyclic mono- and polyenes having at least 3carbon atoms per molecule including cycloalkyl, cycloalkenyl, and arylderivatives thereof; cyclic and polycyclic mono- and polyenes having atleast 4 carbon atoms per molecule including alkyl and aryl derivativesthereof; mixtures of the above olefins; and mixtures of ethylene and theabove olefins. Many useful reactions are accomplished with such acyclicolefins having 3-30 carbon atoms per molecule and with such cyclicolefins having 4-30 carbon atoms per molecule. Nontertiary olefins arethose olefins wherein each carbon atom, which is attached to anothercarbon atom by means of a double bond, is also attached to at least onehydrogen atom. Internal olefins are preferred.

Some specific examples of acyclic olefins suitable for reactions of thisinvention include propylene, 1-butene, 2-butene, 1-pentene, 2-pentene,1-hexene, 1,4-hexadiene, 2-heptene, 1-octene, 2,5-octadiene, 2-nonene,1-dodecene, 2-tetradecene, 1-hexadecene, 1-phenylbutene-2, 4-octene,3-eicosene, 3-hexene, 1,4-pentadiene, 1,4,7-dodecatriene,2-methyl-4-octene, 4-vinylcyclohexane, 1,7-octadiene,1,5,9,13,17-octadecapentaene, 8-cyclopentyl-4,5-dimethyl-1-decene,6,6-dimethyl-1,4-octadiene, and 3-heptene, and the like, and mixturesthereof.

Some specific examples of cyclic olefins suitable for the reactions ofthis invention are cyclobutene, cyclopentene, cycloheptene, cyclooctene,5-n-propylcyclooctene, cyclodecene, cyclododecene,3,3,5,5-tetramethylcyclononene, 3,4,5,6,7-pentaethylcyclodecene,1,5-cyclooctadiene, 1,5,9-cyclodecatriene, 1,4,7,10-cyclododecatetraene,6-methyl-6-ethylcyclooctadiene-1,4, and the like, and mixtures thereof.

The pressure during the disproportionation reaction may vary betweenwide limits. Pressures between 0.1 and 500 atm. are suitable; preferredpressures are between 0.5 and 250 atm. If possible, the process shouldbe operated at a pressure which is atmospheric or nearly atmospheric sothat no vacuum or pressure apparatus is required.

If the reaction is carried out in the liquid phase, solvents or diluentsfor the reactants may be used. Aliphatic saturated hydrocarbons (e.g.,pentane, hexane, cyclohexane, dodecane) and aromatic hydrocarbons suchas benzene and toluene are suitable. If the reaction is carried out inthe gaseous phase, diluents such as aliphatic hydrocarbons (e.g.,methane, ethane) and/or inert gases (e.g., nitrogen, argon) can bepresent. Preferably the disproportionation reaction is effected in thesubstantial absence of reactive materials such as water and oxygen.

The length of time during which the olefinically unsaturated compoundsto be disproportionated are contacted with the catalyst depends uponseveral factors such as the activity of the catalyst, temperature,pressure, and structure of the olefinically unsaturated compound to bedisproportionated. Contact time can conveniently vary between 5 secondsand 24 hours, although longer and shorter contact times may be used. Thecontact time needed to obtain a reasonable yield of disproportionatedproducts depends on the factors mentioned above.

The process of the invention is effected batchwise or continuously, withfixed catalyst beds, slurried catalysts, fluidized beds or by using anyother conventional contacting technique. The solid disproportionationcatalysts are employed in any appropriate form, for example, as powders,flakes, pellets, spheres or extrudates.

The olefinic products of the invention, for the most part, haveestablished utility as precursors of polymers, e.g., as the thirdcomponent of ethylene-propylene terpolymers useful as syntheticelastomers. Cleavage of the ethylenic bonds of polyolefinic products asby ozonization produces di- or polycarboxylic acids which are reactedwith diamines, e.g., hexamethylenediamine, to form Nylons which areuseful in synthetic fibers. The olefinic products are converted tosecondary and tertiary alcohols as by sulfuric acid-catalyzed hydration.Alternatively, the olefinic products are converted by conventional "Oxo"processes to aldehydes which are hydrogenated with conventionalcatalysts to the corresponding alcohols. The C₁₂ -C₂₀ alcohols therebyproduced are ethoxylated as by reaction with ethylene oxide in thepresence of a basic catalyst, e.g., sodium hydroxide, to formconventional detergents and the lower molecular weight alcohols areesterified by reaction with polybasic acids, e.g., phthalic acid, toform plasticizers for polyvinyl chloride.

A further understanding of the present invention and its advantages willbe provided by reference to the following example.

In the example, the tungsten oxide content of the catalyst was 6 weightpercent based on the total weight of tungsten oxide and silica. Thecatalyst was prepared by impregnating high surface area silica with0.0727 gram of ammonium metatungstate (NH₄)₂ W₄ O₁₃.8H₂ O) per gram ofsilica. The impregnation was accomplished by treating the silica with anaqueous solution of the ammonium metatungstate. The impregnated silicawas dried and calcined in air at 500° C. to convert the metatungstate tothe oxide. A -20+40 mesh sieve fraction was obtained for use asdescribed below.

Both runs were made by passing a propylene feed through a verticaltubular quartz reactor (1 cm in diameter and 25 cm in length) positionedin a temperature-controlled electric furnace. In each run the reactorcontained a bed of the designated catalyst. A thermocouple waspositioned in the catalyst bed to monitor reaction temperature. Prior toeach run the catalyst was activated by heating at 600° C. in flowingnitrogen for 0.5 hours.

The propylene feed was of a polymerization grade as sold by PhillipsPetroleum Company of Bartlesville, Okla. The propylene feed waspretreated with activated Alcoa H151 alumina and activated magnesiaprior to the metathesis. The feed was passed downwardly through thevertically oriented tubular reactor. Reaction product analyses were madeby gas-liquid chromatography (glc) employing a Hewlett-Packard model5880A chromatograph having a 1/8 inch by 20 ft. column packed with 19%BMEE+1% squalene on 60/80 Chrom P. Analysis was carried out isothermallyat a temperature of 30° with a helium carrier gas flow rate of about 20mL/min.

EXAMPLE

The reactor was loaded with 2 g of 6% WO₃.SiO₂ catalyst, heated to 600°C. for 1 hour in air, purged with N₂ for 30 minutes, then allowed tocool to 412° C., then propylene flow of about 100 mL/min. at atmosphericpressure introduced. Samples were collected at various time intervalsfor 90 minutes and analyzed for conversion of propylene to ethylene andbutenes. Results are presented in the Table.

Propylene feed was discontinued, the catalyst calcined in air for 30minutes at 600° C., then cooled to room temperature. Once the reactorwas cool, 2 mL of dimethylsulfate was sprayed over the catalyst,unabsorbed liquid allowed to drain, then the catalyst was heated to 600°C. for 90 minutes under a gentle flow of nitrogen. The reactor was thencooled to 412° C. and propylene feed at a rate of about 100 mL/min. atatmospheric pressure introduced. Samples were collected and analyzed asabove. Results are presented in the Table.

                  TABLE                                                           ______________________________________                                                   Conversion, %                                                                 time, minutes                                                      Catalyst     5     15      30   45    60   90                                 ______________________________________                                        Untreated    1.5   3.5     4.1  4.6   5.2  6.0                                (CH.sub.3 O).sub.2 SO.sub.2 added                                                          5.1   8.5     10.6 12.3  13.5 15.4                               ______________________________________                                    

The results of these experiments demonstrate the enhanced propyleneconversion achieved with dimethylsulfate treated WO₃.SiO₂ catalyst.

What is claimed is:
 1. A process for disproportionating olefinscomprising contacting at least one feed olefin having at least 3 carbonatoms per molecule under suitable reaction conditions which convert thefeed olefin into other olefins having different numbers of carbon atomswith a catalytically effective amount of a catalyst compositioncomprising an inorganic refractory oxide and at least one metal oxideselected from molybdenum oxide and tungsten oxide promoted with aneffective promoting amount of a methylating agent.
 2. A processaccording to claim 1 wherein said inorganic refractory oxide is selectedfrom silica, alumina, and mixtures thereof.
 3. A process according toclaim 2 wherein said catalytic amount of said metal oxide is in therange of about 1 to about 20 percent of the combined weights of saidmetal oxide and said refractory oxide prior to the addition of themethylating agent.
 4. A process according to claim 3 wherein thedisproportionation is carried out at a temperature in the range of about20° C. to about 600° C.
 5. A process according to claim 4 wherein themethylating agent is employed in an amount in the range of about 0.1 toabout 20 weight percent based on the weight of the metaloxide-refractory oxide combination prior to the addition of themethylating agent.
 6. A process according to claim 5 wherein said metaloxide is WO₃ and said refractory oxide is SiO₂.
 7. A process accordingto claim 6 wherein said methylating agent is dimethyl sulfate.
 8. Aprocess according to claim 1 wherein said feed olefin comprisespropylene.
 9. A process according to claim 1 wherein the olefin feedadditionally contains ethylene.
 10. A process according to claim 7wherein said feed olefin comprises propylene.